Plibersek was elected to the House of Representatives for Sydney in 1998 and re-elected five times.[5] She was elected to the Shadow Ministry after the 2004 election. She was Shadow Minister for Work, Family and Community, Shadow Minister for Youth and Early Childhood Education and Shadow Minister Assisting the Leader on the Status of Women since October 2004. This portfolio was retitled Shadow Minister for Child Care, Youth and Women in June 2005. Following the Shadow Ministerial reshuffle in December 2006 (when Kevin Rudd assumed the leadership of the Federal Parliamentary Labor Party) Plibersek was promoted to be Shadow Minister for Human Services, Housing, Youth and Women.

As Minister for Housing, Plibersek launched the Social Housing Initiative, which provided for the construction of more than 19,300 new social housing units, with approximately 70,000 units receiving repairs and maintenance.[8] In December 2008, along with Kevin Rudd, Prime Minister at that time, Plibersek released the Government's White Paper on Homelessness, The Road Home, which has a goal of halving homelessness by 2020.[9]

Plibersek is a member of EMILY's List Australia, a political group that supports candidates, who in turn support Emily's List's views on equity, childcare, equal pay, diversity and reproductive freedom,[10] to be elected to political office.[11][12]

As Minister for Health, Plibersek approved listing the abortion drugRU-486 on the Pharmaceutical Benefits Scheme. Plibersek described the provision of the medicine as "a good thing in the situation where women are faced with one of the most difficult decisions that they will ever make".[13]Anti-abortion groups criticised the move, with one campaigner, Margaret Tighe, labelling it a "gross abuse of power."[14] Other commentators, including Clementine Ford, labelled the decision "progressive".[15][16]

As Minister for the Status of Women in the Rudd Labor Government, Plibersek initiated policies such as convening the National Council to Reduce Violence against Women and their Children in May 2008, and releasing the National Council's Plan for Australia to Reduce Violence Against Women and their Children in March 2009.[17][18] Plibersek also addressed the 2009 United Nations International Women's Day event, attended by United Nations Secretary General Ban Ki-moon, and announced Australia's formal accession to the United Nations Optional Protocol to the Convention on the Elimination of All Forms of Discrimination Against Women (CEDAW).[19] Plibersek said that acceding to the Optional Protocol "will send a strong message that Australia is serious about promoting gender equality and that we are prepared to be judged by international human rights standards."[20]

Plibersek campaigned for the removal of discrimination against same-sex de facto couples in federal legislation, raising the issue formally in Parliament on multiple occasions (including 1999),[21] 2006,[22] and 2008[23] over her parliamentary career. In her regular paid advertisement in the South Sydney Herald, in 2010 Pliberek wrote that 'The passing of these reforms to federal legislation was one of the proudest moments of my time in the Australian Parliament'[24] and has marched in the Sydney Gay and Lesbian Mardi Gras Parade in 2008.[25] The Labor Party was criticised by some LGBT groups[26][27] over the party's bipartisan policy against the legalisation of same-sex marriage. Plibersek's own views aside, in 2007 she told The Sydney Morning Herald[28]

Labor does not support changing the Marriage Act to allow same-sex marriage.

On 25 July 2004, Plibersek was loudly heckled at an anti-homophobia rally due to the issue.[27]

At the Australian Labor Party national conference in 2011, the delegates voted to include same-sex marriage as official party policy, although MPs are allowed a conscience vote.[29]

Plibersek opposed the 2003 invasion of Iraq.[30] It was reported that when US President, George W. Bush, visited the Australian Parliament in 2003, 'Sydney Labor MP Tanya Plibersek walked around the chamber as President Bush shook hands with MPs to give Bush's national security adviser Condoleezza Rice a book of speeches by Labor MPs opposing Australia invading Iraq without UN approval.'[31] She also stated in Parliament, "I do not support an attack on Iraq. I particularly do not support a pre-emptive first strike. Nor do I support any action that is initiated by the US alone rather than being sanctioned by the United Nations."[30]

Speaking under parliamentary privilege in the House of Representatives on 17 September 2002, Plibersek said: "I can think of a rogue state which consistently ignores UN resolutions, whose ruler is a war criminal responsible for the massacres of civilians in refugee camps outside its borders. The US supports and funds this country. This year it gave it a blank cheque to continue its repression of its enemies. It uses US military hardware to bulldoze homes and kill civilians. It is called Israel, and the war criminal is Ariel Sharon. Needless to say, the US does not mention the UN resolutions that Israel has ignored for 30 years; it just continues sending the money..."[32]

Plibersek lives in Sydney with her husband, Michael Coutts-Trotter who is a senior public servant and the current director-general of the New South Wales Department of Family and Community Services,[37] and their children Anna, Joseph and Louis.[38]

Following the 2010 federal election where Labor retained government with the support of the Australian Greens and independents, parliamentary numbers were finely balanced. Plibersek was granted a pair by the Coalition so that her absence from the House of Representatives while on maternity leave did not affect the result of votes.[39] She gave birth to a son on 1 October 2010.[40][41]